In recent years, due to rise of environmental protection and global warming, the green industry has been greatly developed. Solar cells are a major technology in the green industry. Methods for developing a high efficiency, low-cost solar cell have become an important focus of research. Solar cells can be disposed on buildings, such as houses, and movable apparatus, such as cars; indoors, or on portable electric devices, to convert light into electrical power.
The conventional art develops solar cells with selective emitters. Emitters with a low concentration between electrodes can reduce the recombination of carriers at the surface of the cell, while emitters with a higher doping concentration under electrodes can provide good contact. Therefore, compared to conventional solar cells with emitting structures that have a constant doping concentration, solar cells with selective emitters have higher open loop voltage (Voc) and short-circuit current (Isc) and thus higher photoelectric conversion efficiency.
In 2010, Sunpower Company developed a solar cell with a back electrode having a cross-finger shape and an efficiency of 24.2%. Although this solar cell has a good conversion efficiency, it has a very high manufacturing cost due to its requiring many high-temperature and photolithography processes.
Both the solar cells with selective emitters and the solar cells with a back electrode having a cross-finger shape employ patterned doping regions to increase conversion efficiency. However, the process for forming patterned doping regions is more complicated and requires a highly accurate process, such as lithography, thus increasing the cost of the solar cell.